otto docker — stacks on lab hosts¶

otto docker builds images and orchestrates compose stacks on docker-capable lab hosts, not on the machine otto runs on. Everything rides the host subsystem: builds and compose commands execute over the parent host’s existing SSH connection (hops included), which is the parent-delegation design covered in Design: Docker container hosts.

The compose lifecycle¶

Container hosts have a two-stage life:

1. Declared. At lab load, every service declared in a repo’s [docker] settings is registered as a placeholder DockerContainerHost (id <parent>.<project>.<service>). Placeholders make --list-hosts and completion work before anything is running, and turn “no such host” into a precise “run otto docker up first.”

2. Live. compose up resolves real container ids and overwrites the placeholders; compose down closes each container host before its parent’s connection (sessions must drain while the transport is alive — the ordering rule from The command lifecycle) and restores the placeholders. hosts.json is never written back — lab data stays read-only.

What is unique about docker¶

• Content-addressed build skipping. Images are tagged with a hash of the Dockerfile, build context (after .dockerignore), build args, and target stage; docker image inspect on the tag short-circuits a rebuild, and the hash is computed on the otto side so it stays correct across parents. --rebuild forces.

• No reservation gate of its own (gate=False): a container has no independent reservation — the parent host’s reservation transitively covers its containers, so gating the parent is the whole story.

otto docker --help¶